The present application relates to a method for forming an electrode structure for use in a light emitting device and a method for forming a stacked structure.
A light emitting device composed of, for example, a light emitting diode, generally has a stacked structure including a substrate, a first compound semiconductor layer of a first conduction type, an active layer, and a second compound semiconductor layer of a second conduction type. The first compound semiconductor layer, the active layer, and the second compound semiconductor layer are stacked on the substrate. The substrate or first compound semiconductor layer includes a first electrode formed thereon and the second compound semiconductor layer includes a second electrode formed thereon. With respect to the light emitting device, there have been known a light emitting device of a type such that light generated by the active layer passes through the second compound semiconductor layer and is emitted (hereinafter, frequently referred to as “light emitting device of type 2”) and a light emitting device of a type such that the light passes through the first compound semiconductor layer and is emitted (hereinafter, frequently referred to as “light emitting device of type 1”). In the light emitting device of type 1, from the viewpoint of achieving improved light emission efficiency, it would be desirable that light generated by the active later passes through the second compound semiconductor layer and is reflected by the second electrode. Accordingly, silver (Ag) having a high optical reflectance is frequently used as the second electrode.
Silver (Ag) is likely to cause ion migration. When ion migration is caused in the second electrode composed of silver, short-circuiting disadvantageously occurs between the first compound semiconductor layer and the second compound semiconductor layer, so that it becomes that the active layer does not emit light.
A technique for preventing the ion migration has been known from, for example, Japanese Unexamined Patent Application Publication No. 11-220171. This patent document discloses a gallium nitride compound semiconductor device including a second electrode (p-side electrode) having a structure such that a first material layer composed of silver (Ag) is covered with a second material layer.